linux-kernel - Re: [PATCH v4 18/20] ACPI: platform

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Message-ID: <42623eed-1220-4cdf-aa7f-3a9777a3da4b@gmx.de>
Date: Wed, 6 Nov 2024 20:21:01 +0100
From: Armin Wolf <W_Armin@....de>
To: Mario Limonciello <mario.limonciello@....com>,
 Hans de Goede <hdegoede@...hat.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
 Maximilian Luz <luzmaximilian@...il.com>, Lee Chun-Yi <jlee@...e.com>,
 Shyam Sundar S K <Shyam-sundar.S-k@....com>,
 Corentin Chary <corentin.chary@...il.com>, "Luke D . Jones"
 <luke@...nes.dev>, Ike Panhc <ike.pan@...onical.com>,
 Henrique de Moraes Holschuh <hmh@....eng.br>,
 Alexis Belmonte <alexbelm48@...il.com>,
 Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
 Ai Chao <aichao@...inos.cn>, Gergo Koteles <soyer@....hu>,
 open list <linux-kernel@...r.kernel.org>,
 "open list:ACPI" <linux-acpi@...r.kernel.org>,
 "open list:MICROSOFT SURFACE PLATFORM PROFILE DRIVER"
 <platform-driver-x86@...r.kernel.org>,
 "open list:THINKPAD ACPI EXTRAS DRIVER"
 <ibm-acpi-devel@...ts.sourceforge.net>,
 Mark Pearson <mpearson-lenovo@...ebb.ca>,
 Matthew Schwartz <matthew.schwartz@...ux.dev>
Subject: Re: [PATCH v4 18/20] ACPI: platform_profile: Allow multiple handlers

Am 05.11.24 um 16:33 schrieb Mario Limonciello:

> Multiple drivers may attempt to register platform profile handlers,
> but only one may be registered and the behavior is non-deterministic
> for which one wins.  It's mostly controlled by probing order.
>
> This can be problematic if one driver changes CPU settings and another
> driver notifies the EC for changing fan curves.
>
> Modify the ACPI platform profile handler to let multiple drivers
> register platform profile handlers and abstract this detail from userspace.
>
> To avoid undefined behaviors only offer profiles that are commonly
> advertised across multiple handlers.
>
> If any problems occur when changing profiles for any driver, then revert
> back to the balanced profile, which is now required.

Reviewed-by: Armin Wolf <W_Armin@....de>

> Tested-by: Matthew Schwartz <matthew.schwartz@...ux.dev>
> Reviewed-by: Mark Pearson <mpearson-lenovo@...ebb.ca>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>   drivers/acpi/platform_profile.c | 12 ++----------
>   1 file changed, 2 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/platform_profile.c
> index 568485e285061..b9eb25f58a2a2 100644
> --- a/drivers/acpi/platform_profile.c
> +++ b/drivers/acpi/platform_profile.c
> @@ -10,7 +10,6 @@
>   #include <linux/platform_profile.h>
>   #include <linux/sysfs.h>
>
> -static struct platform_profile_handler *cur_profile;
>   static DEFINE_MUTEX(profile_lock);
>
>   static const char * const profile_names[] = {
> @@ -368,8 +367,7 @@ static const struct attribute_group platform_profile_group = {
>
>   void platform_profile_notify(void)
>   {
> -	if (!cur_profile)
> -		return;
> +	guard(mutex)(&profile_lock);
>   	if (!class_is_registered(&platform_profile_class))
>   		return;
>   	sysfs_notify(acpi_kobj, NULL, "platform_profile");
> @@ -428,9 +426,6 @@ int platform_profile_register(struct platform_profile_handler *pprof)
>   	}
>
>   	guard(mutex)(&profile_lock);
> -	/* We can only have one active profile */
> -	if (cur_profile)
> -		return -EEXIST;
>
>   	if (!class_is_registered(&platform_profile_class)) {
>   		/* class for individual handlers */
> @@ -451,9 +446,9 @@ int platform_profile_register(struct platform_profile_handler *pprof)
>   	if (IS_ERR(pprof->class_dev))
>   		return PTR_ERR(pprof->class_dev);
>   	dev_set_drvdata(pprof->class_dev, pprof);
> +
>   	sysfs_notify(acpi_kobj, NULL, "platform_profile");
>
> -	cur_profile = pprof;
>   	return 0;
>
>   cleanup_class:
> @@ -467,13 +462,10 @@ int platform_profile_remove(struct platform_profile_handler *pprof)
>   {
>   	guard(mutex)(&profile_lock);
>
> -	cur_profile = NULL;
> -
>   	sysfs_notify(acpi_kobj, NULL, "platform_profile");
>
>   	device_destroy(&platform_profile_class, MKDEV(0, pprof->minor));
>
> -	cur_profile = NULL;
>   	return 0;
>   }
>   EXPORT_SYMBOL_GPL(platform_profile_remove);